PATIENT CHARACTERISTICS: Age: 16 and over Performance status: ECOG 0-2 Life expectancy: Not specified Hematopoietic: Not specified Hepatic: Bilirubin no greater than 2.0 mg/dL AST or ALT less than 3 times upper limit of normal Renal: Creatinine no greater than 1.5 mg/dL OR Creatinine less than 1.8 mg/dL if creatinine clearance at least 45 mL/min Other: No known hypersensitivity to troxacitabine or its analogues No active uncontrolled serious infection No other severe medical condition that would preclude study No neurologic or psychiatric disorders that would preclude informed consent No uncontrolled underlying medical condition or underlying condition that could be aggrevated by treatment Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception